1. Technical Field
The present disclosure relates to a suspension member for a vehicle used in a suspension that suspends a wheel relative to a vehicle body.
2. Description of Related Art
A suspension member for a vehicle is provided between a wheel and a vehicle body, and thus various loads, such as a load inputted from a road surface via the wheel, a load inputted from the vehicle body, and a load inputted from a steering mechanism, act on this suspension member. Hence, the suspension member is required to have an appropriate rigidity against such loads. For example, as an example of such a suspension member, there has been known a front knuckle (hereinafter, referred to as a knuckle). FIG. 9A is a front view of a knuckle 100, and FIG. 9B is a side view of the knuckle 100. The knuckle 100 includes a body part 110 having a circular hole 111 into which a hub bearing is installed formed by piercing the body part 110, and a neck part 120 so formed to integrally extend upward from the body part 110. An upper end of the neck part 120 is coupled to the vehicle body via an upper arm. A lower-end center 150 of the body part 110 is coupled to the vehicle body via a lower arm, and one lower end 170 of the body part 110 is coupled to a steering mechanism via a tie rod. The knuckle 100 is made of metal, such as iron and aluminum, and is produced by forging or casting. In FIG. 9, members coupled to the knuckle 100 are not illustrated.
A load in a torsional direction acts on the neck part 120 of the knuckle 100 as indicated by an arrow a of FIG. 9B, and a load in a bending direction acts on the body part 110 as indicated by an arrow b of FIG. 9A. In the knuckle 100 of related art, rigidity against the load in the torsional direction and rigidity against the load in the bending direction are secured by a sectional shape of the knuckle 100. If a product is produced by using an isotropic material, a torsional rigidity kT in a portion having a rectangular section (long side x, short side y) as shown in FIG. 10 is represented by the following formula, for example.kT=G×k×x×y3 where G represents a modulus of longitudinal elasticity, and k represents a coefficient, (x>y).
Accordingly, in order to enhance the torsional rigidity, it is optimum to increase a dimension of the short side y as shown in FIG. 10B. If there is any restriction on increasing in dimension of the short side y, it is also possible to enhance the torsional rigidity by increasing the dimension of the long side x; but in this case, increase in mass becomes too great, which is not unfavorable.
In light of limitation of space, the suspension member has restriction on its shape in order to avoid interference with other components. For example, as shown in FIG. 9B, a shock absorber S is disposed inward of the knuckle 100 (inward in the vehicle-width direction), and a tire T is disposed outward of the knuckle 100 (outward in the vehicle-width direction). Consequently, it is restricted to increase a thickness of the knuckle 100 in the vehicle-width direction. Hence, it is difficult to efficiently enhance the rigidity by the sectional shape of the knuckle 100, and increase in mass is likely to be caused.
Meanwhile, for example, in International Publication No. 2012/137554, there is proposed an automobile component produced by using a carbon fiber composite material. The composite material proposed in WO 2012/137554 A is a structural material formed by joining a unidirectional composite material in which reinforced fibers are orientated in one direction and a random composite material in which reinforced fibers are randomly orientated to each other.